Tree delimbing devices are generally known in the prior art of the forestry and tree harvesting industry. These delimbers typically utilize stripping arms and guide arms to facilitate the delimbing operation. A felled tree is moved longitudinally through a support frame of a delimber which supports the arms that guide and subsequently strip the outwardly extending limbs of the tree. A knuckle boom loader is normally used to grasp and move the tree through the delimbing device. When the delimbing process is completed the stripped trunks of the felled trees may be placed on a transport trailer by the knuckle boom loader.
Uniform inward and outward movement of the stripping and guide arms is required to maintain the felled tree in a centered position within the support frame of the delimber. A centered position of the felled trees is required for an efficient delimbing operation. Stripping arms may gouge the trunk of a felled tree which has not been properly centered as it is moved through the delimber, thereby impairing the forward longitudinal movement of the tree and delaying the entire delimbing process.
In the past, delimbers have utilized different means for providing uniform inward and outward movement of the stripping and guiding arms. Resilient springs were often used as a method of moving the arms inward and to maintain the arms against the trunks of the felled trees. Positive gear drives, such as those found in U.S. Pat. No. 4,749,012 issued to Hamby, have also been used to control the inward movement of the stripping and guide arms in other delimbing machines. These gears are drivingly interconnected to time mechanically the closing of one arm with another. Such gearing means adding a great deal of manufacturing expense to the delimbing apparatus. Often, hydraulically activated cylinders are used to move these stripping and guiding arms to their open position, while the resilient means control the inward movement to maintain the arms against the tree trunk when the hydraulic cylinder rods are extended. In my U.S. Pat. No. 5,293,914, I addressed a need for a controlled independent uniform operation of these stripping and guide arms to allow for efficient consistent delimbing operations. Experience in using delimbers with various types of trees has led to the realization that closure of the guide arms and stripping arms creates problems on trees with trunks that are deformed, such that the trunk binds between the guide arms and the stripping arms such that the freely pivoting delimber head is unable to follow the trunk and, therefore, improperly delimbs the tree. That is to say, it gouges the tree or it requires excessive force to pull the tree through the delimber, thereby unnecessarily stressing the loader and support structure.